The present invention relates to a metal gasket with a peripheral bead to provide as a whole a surface pressure as equal as possible.
In a cylinder head gasket for an internal combustion engine, a plurality of cylinder bores is often arranged linearly. In this case, the cylinder bores may not be arranged in the center of the gasket because of various reasons, such as arrangements of push rod holes, cam shafts and the like on one side of the engine (Japanese Utility Model Publication (KOKAI) No. 3-77053).
On the other hand, the engine is provided with water holes, oil holes, bolt holes and so on in addition to the cylinder bores. In the gasket situated between a cylinder head and a cylinder block, therefore, sealing means for the cylinder bores, water holes and oil holes are formed. In this case, since high pressure is formed inside the cylinder bores, the bolt holes are arranged around the cylinder bores to securely seal therearound. Other holes are situated near the cylinder bores, and the sealing means for other holes are compressed by the bolts for the cylinder bores.
Therefore, although the sealing means for the cylinder bores receive the relatively equal tightening pressure, the sealing means for other holes do not have equal tightening pressure. In case the cylinder bores are not located in the center of the gasket, the other holes and the sealing means thereof are not arranged symmetrically relative to the longitudinal direction of the cylinder bores, so that the sealing means for the other holes are not equally compressed. In order to securely seal around the other holes, it is preferable to provide an equal tightening pressure to the sealing means for the other holes.
In U.S. Pat. No. 4,834,399, a gasket is provided with a bead around an outer periphery of the gasket to secondarily seal around the gasket. In other patents, a bead portion away from a bolt, which receives a surface pressure less than that near the bolt, has another bead portion or is made narrow to provide a high surface pressure. However, there has not been known that the gasket is processed to provide a tightening pressure as a whole as equal as possible.
Accordingly, one object of the invention is to provide a metal gasket, which can provide a tightening pressure as a whole as equal as possible in case a hole is arranged eccentrically.
Another object of the invention is to provide a metal gasket. as stated above, wherein sealing means of fluid holes receive tightening pressures substantially equally.
A further object of the invention is to provide a metal gasket as stated above, wherein all the sealing means can be securely sealed.
Further objects and advantages of the invention will be apparent from the following description of the invention.